Boiler



March 2, 1937. o. H. HARTMANN BOILER Filed March 24, 1956 INVENTOR 07 70 H. HflATN/i/V/V BY ATTORNEY I slope.

Patented Mar. 2, 1937 UNITED STATES PATENT OFFICE many, assignor to Schmidtsche Heissdampf- Gesellschaft, m. b. H., Kassel-Wilhelmshohe,

Germany Application March 24, 1936, Serial No. 70,589 In Germany April 18, 1935 4 Claims.

The invention relates to a coil boiler with nat ural circulation whose water tube coils comprise a section lining the combustion chamber and exposed to radiant heat, and a section heated by convection and located in the path of the gases leaving the combustion chamber. This combination of evaporating surface which is heated by convection with evaporating surface which is heated by radiant heat makes possible an efiicient utilization of the heat liberated in the furnace.

In accordance with the invention the furnace wall is lined by a plurality of pipe coils arranged for flow in paralle and spiralling in multipitch upward along the furnace wall, and each of these coils is connected to a steam-and-water drum or header by means of a serpentine or zigzag coil comprising tube lengths extending through the pass above the combustion chamber at substantially uniform slope and connected by means of return bends lying in substantially horizontal position.

In the drawing is shown an illustrative example of the new boiler.

Fig. 1 is a vertical section; Fig. 2 is a front view; Figs. 3 and 4 are cross sections on lines 3-3 and 4-4 respectively of Fig. 1; Fig. 5 is a lateral view with a portion in vertical section of the lower part of a modified form and Fig. 6 is a front view of the form shown in Fig. 5.

The boiler is shown as a single-pass boiler. From the furnace I, which by way of illustration is shown as equipped with an oil burner 2, the products of combustion flow through the vertical pass 3 toward the outlet 4. This pass is, in the form shown, square in cross section but could of course be given some other form, for example rectangular, or polygonal with more than four sides, or circular. The lower portion of the vertical pass is enclosed by the tubular lining formed by four coils connected in parallel. Thus each of the coils 5 spirals upward around the combustion space and at its upper end connects with a serpentine or zig-zag coil extending across the pass. The return bends in these lastnamed coils lie in a generally horizontal position in order to secure a continuous gradual upward At the point where the spiral coils are connected to the zig-zag coils the pipes are preferably bifurcated. The two branches of the bifurcated part form two groups of serpentine or zig-zag coils, 6 and 1, arranged side by side and relatively staggered so that a comparatively restricted passage is left for the gases. These coils open into the steam and water drum 9 located outside of the housing 8 of the boiler. From the drum 9 a number of downcomers l8, equal in number to the coils 5, lead to the lower ends of these coils. These downcomers lie within the sheet 8 but outside of the tubular lining formed by the coils 5, so that they are protected against the heating gases. At the lower end of each coil 5 and suitably at the point Where the downcomers I connect with the lowest portion of the coils 5, there are fitted blow-off cocks 12. The coils 6, 1 are provided with cleanout plugs 13 which lie outside of the casing 8 of the boiler so that they are readily accessible. In the portion of the pass above the convection coils 6, I is arranged the superheater M which receives steam from header 9 and from which steam is led to the point of consumption.

The single pass boiler described above presents a very simple construction. The individual coils all have substantially the same length and they are all heated to substantially the same extent. The upward slope is substantially constant for the entire length of the coil. Sudden changes in direction or slope are entirely avoided so that the very effective evaporating surface offers small resistance to the upward flow of the steam and water mixture. This constitutes an advance over coil boilers as built heretofore in which the return bends lie in vertical planes and have a short radius causing a rapid reversal of flow. Evaporating tubes of the earlier form offer such high resistance to flow that the steam and water mixture can be forced upward only by violent pulsations. This means that large amounts of water are carried along into the upper drum and the steam is correspondingly wet. In a steam generator according to the present invention the water carried along by the steam may be said to be pushed up along a gently sloping surface, the separation of the steam from the water occurring during the upward travel. The steam taken off from the drum is therefore relatively dry.

Instead of connecting each downcomer directly to the lower end of its coil as described, the connection might be made indirectly through an intermediate small header. A form of this kind is illustrated in Figs. and 6 where the lower header is indicated by the reference numeral 15. This header is equipped with a blow-off cock l6 and preferably the same number of downcomers Hi open into it as there are coils 5, e. g. in the illustrated case there are four of each. The circulation through the several evaporating coils is in this form not independent to the same degree as in the form according to Figs. 1 to 4. The heating of all of the coils is however very even and this ensures their all receiving their share of water, and there will be no danger of burning up any of the coils through lack of water.

The new boiler is particularly suitable, on account of its compactness, for use on vehicles. It may, moreover, be used as the evaporating portion of the closed circuit in an indirect steam generator such as that shown in United] States Patent 1,788,520 1931, or may be for consumption.

What I claim is: v

1. A coil boiler with natural circulation comprising a plurality of coils extending in parallel spirals along the inner walls of the combustion chamber of the furnace, a steam-ancl-water drum some distance above the furnace, a serpentine coil connecting the upper end of each spiral coil to the steam-and-water drum, each of said used to furnish steam directly granted tome on January 13,

serpentine coils comprising straight tube lengths extending at substantially the same upward slope through the space above the combustion chamber and connected by means of substantially horizontal return bends, and downcomers connected to convey water from the steam-and-water drum to the lower ends of the spiral coils.

2. Apparatus in accordance withclaim 1, the serpentine coils each comprising two branches the straight lengths of one branch being staggered relatively to those of the other branch.

3. Apparatus in accordance with claim 1, the number of downcomers being the same as that of the coils and each downcomer being connected directly to the lower end of the spiral coil.

4. Apparatus in accordance with claim 1, and.

further comprising a lower header to which both the downcomers and the lower ends of the spiral coils are connected.

OTTO H. HARTMANN. 

